OneToMany关系。如何提出要求?
问题描述:
你好。我是SQL中的noob,所以将appriciate,如果你帮我写一个SQL请求获取FINALSCORE字段FROM tennisset表,与tennismatch相关WHERE id = 1
谢谢。
答
尝试此查询:
select FINALSCORE from
tennismatch join
tennismatch_tennisset on tennismatch.ID = tennismatch_tennisset.TennisMatch_ID and tennismatch.ID = 1 join
tennisset on tennismatch_tennisset.mapOfSets_ID = tennisset.ID
从表“tennismatch”删除记录,首先删除子表“tennismatch_tennisset”的记载。
尝试这样:
delete from tennismatch_tennisset where TennisMatch_ID =1
delete from tennismatch where id=1
答
您需要使用表之间的连接。在你的情况下,它必须通过tenismatch_tenisset这是两者之间的绑定表完成。
select finalscore from tennismatch m
join tenismatch_tennisset ms
on m.id = ms.tennismatch_id
join tennisset s
on ms.mapofsets_id = s.id
where m.id = 1
如果有人为你写查询,你不会得到更好的结果。 –
我相信我会的,只需要了解如何去做。迈出第一步。 –
您应该从[SELECT](https://www.w3schools.com/sql/sql_select.asp)开始,然后继续[JOIN](https://www.w3schools.com/sql/sql_join.asp)然后进入如果您仍然卡住,那么返回您的代码。另请阅读如何准备[mcve] –